Distributed generation capacity under net metering grew from essentially zero to a median of 33.5 MW per utility in 2024. PG&E now hosts 8,889 MW of distributed solar — more installed capacity than many utility-scale solar farms. This is generation that sits behind the meter, reduces grid sales, and creates complex cost allocation challenges that regulators are still working through.
The average system size — capacity divided by NM customers — reveals the market structure. Early net metering was dominated by small residential systems of 3-5 kW. As commercial and industrial customers began participating, average system sizes grew. SDG&E at 6.97 kW average reflects a mature residential market. A utility with unusually high capacity per customer has significant commercial solar participation.
For load planners and rate designers, distributed generation capacity is a critical input to long-run forecasting. The combination of T-22 load trends, T-36 net metering customers, and T-37 installed capacity provides the complete picture of how distributed solar is reshaping utility load profiles and creating both opportunities and challenges for grid planning.
| Utility | Installed Capacity (MW) | Avg System Size (kW) | Penetration Rate | Capacity Growth 2008→2024 |
|---|
| Year | Installed Capacity (MW) | Penetration Rate |
|---|---|---|
| 2024 | — | — |
| 2023 | — | — |